He is on the verge of becoming the most successful racing trainer in British history.

But as Mark Johnston races to just a nose behind the all-time record of 4,193 racing wins, it is a long way from his modest start in racing, at a stables south of Grimsby when his wife taught in the town to help pay the bills.

Johnston, a Scot, secured his first training licence in 1987 and bought the small Bank End Stables in North Somercotes, with just enough room for a handful of horses.

Johnston and his wife Deirdre risked everything on the venture, accepting a £5,000 loan from his dad and a mortgage of £45,000 with an overdraft of £15,000.

Training the horses on the nearby Donna Nook beaches – when the RAF weren’t using it as a bombing range or hundreds of seals were coming ashore – Johnston managed to secure just one win in the couple’s first year.

And as he and Deirdre struggled to make money from their new venture, she combined training with a job teaching in Grimsby to help the couple find their feet.

As her husband closed on the remarkable achievement, Deirdre recalled: “In those early days we were so short of money I worked as a teacher in Grimsby.

"I used to ride out, go to work and then come back and do evening stables.”

Trainer Mark Johnston at his first stables in North Sommercotes near Grimsby (Image: johnstonracing.com)

Johnston, then 27, and a qualified vet, would also carry out work for other stables and farms to supplement their income.

He said: “We knew that the worst thing that would happen was that we would lose it all and end up back working as a teacher and a vet to pay off the debt.’

Mark told the Racing Post: “We started off right at the bottom with three and a half paying horses but with the ambition to train lots of winners, including Classic winners.

“We were so small it's hard to imagine what we've achieved. In our first year we had one winner and in the second only five."

Deirdre Johnston with Mark. She worked as a teacher in Grimsby when the couple set up their first stable (Image: johnstonracing.com)

After his first win, when Hinari Video won at Carlisle, Johnston recalled how he and Deidre turned to teletext as at the time it was the only way to follow racing as it happened as few were televised.

Johnston said: "The most abiding memory is coming home and putting the results on Teletext and having nothing else on the television all night.

"There were no racing channels in those days, no replays, and if you wanted a video you had to send off for one and it came in about three weeks' time. So we watched Teletext all night!"

Johnston later described his time on the Lincolnshire coast as “the coldest place on Earth.”

He said: "It was all reclaimed land around there and completely flat too. The wind used to blow straight in from Russia.”

Mark would train his small number of horses at nearby Donna Nook beach.

He said: “I remember there were two telegraph poles which we reckoned were two furlongs apart. I used to climb up one of them to get a better view of the horses working!”

But visits to the beach had to be carefully planned to avoid the RAF practice bombing raids.

But soon there were signs of Johnston’s natural talent as a trainer, developing a style for his horses to run from the front and dig in for the finish.

The second year saw five winners, and the couple were able to move from North Somercotes to buy Kingsley House in Middleham in North Yorkshire, where the couple are still based and now employ more than 100 staff with stables for almost 250 horses.

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And following that first win, Johnston has turned the project that started off with loans and mortgages into a multi-million pound business, the winnings from his horses alone worth more than £50m.

It has funded a comfortable lifestyle, including a private plane he flies himself to meets, but regarded by the racing industry as one if the most deserved in the sport.

Trainer Mark Johnston is poised to become Britain's most successful racing trainer in history (Image: PA)

But from his first winner from North Somercotes to his record breaking run towards the existing British record of 4,193 winners, which he is expected to reach within days, he still has a single focus in the sport.